Currently it is common to view or edit images, which are sensed by a digital camera, by employing application software installed in a personal computer (PC).
Some digital cameras have a function for storing a sensed image as raw data (data that has been subjected to photoelectric conversion by an image sensor such as a CCD or a CMOS, then subjected to A/D conversion and lossless compression at the time of image sensing by a digital camera, thus keeping the sensed information intact). Hereinafter, an image stored as raw data will be referred to as a raw image.
Further, some image processing software is capable of image processing (hereinafter referred to as raw image development processing) based on image processing parameters (hereinafter referred to as development parameters), e.g., attribute information recorded in association with the raw image, characteristics of the digital camera main unit, as well as resolution, sharpness, hue, and white balance set by a user.
Employing such image processing software enables a user to obtain an image of which the quality meets the user's preferences with its parameters adjusted. Note that since image data that has been developed is generally stored in a versatile data type (JPEG, BMP, TIFF or the like), processing including storage may be referred to as development processing.
For instance, according to the disclosure of Japanese Patent Application Laid-Open (kokai) No. 2004-080099, development processing is performed on raw image data by applying development parameters, e.g., white balance adjustment, color-effect mode selection, contrast adjustment, color-density adjustment, sharpness adjustment and so on set by a user, and the developed result is displayed on a display device and stored in a versatile file such as JPEG.
However, in raw image development processing, the outcome of image development using the inputted development parameters is unknown until the user sees the actual result of development. Therefore, it is difficult to achieve a satisfactory processing result without inputting parameters two or more times. Normally, a user repeats parameter input by trial and error, while confirming the developed result on the display device, to determine satisfactory parameter values.
Since each processing that constitutes development processing applying the user-input development parameters is performed on all pixels of raw image data (in principle, their number is the number of effective pixels of the image sensor), the processing load involved in the development processing is very heavy or high. If development is performed each time the parameter value is changed in the process of trial and error to decide the development parameter values, an extremely long processing time is required.
Furthermore, along with the trend toward higher resolution of a digital camera in recent years, the processing load has tended to become heavy. In addition, due to users' rising interest in higher image quality, image processing on raw image data is growing popular.